Shock absorber for landing gears for aeroplanes



May 20, 1930. J. F. WALLACE 1,759,674

SHOCK ABSORBER FOR LANDIUG GEARS FOR AEROPLARES F1104 April 8,1926 2 Sheets-Sheet 1 May 20,1930. J. F. WALLACE SHOCK ABSORBER FOR LANDING GEARS FOR AEROPLANES Filed April 8, 1926 2 'Shegts-Sheet 2 Patented -May 20, 1930 UNITED STA ES PATEN T OFFICE JOHN F. WALLACE, or SHAKER HEIGHTS, o'nro, ssrcnoa TO THE CLEVELAND PNEU- MATIC TOOL COMPANY, or CLEVELAND, OHIO, A CORPORATION or omo snocx ABSORBER roaLANDme GEARS r03. AEBOPLANES Application filed April a, 1926. Serial No. 100,521.

This inventionrelates to a shock absorber adapted particularly for an aeroplane landing gear and has for its chief object to provide a shock absorbing member preferably v tl e ground or deck 'of a ship ride over an n' the form of a strut which will absorb the shock which would otherwise be transmitted to the aeroplane itself when the plane makes a landing on ground, water or deck of a ship.

A further object is to provide a shock absorbing element in the landing gear so formed as to absorb the shock, prevent sudden rebound and at the same time enable the absorption of shocks should the plane strike repeatedly or in quick succession on landing or should the plane immediately on striking obstruction.

' avoid being subjected to lateral stresses when i nectlons or the equivalent of universal. con- The shock absorbing device formed in ac-' co'rdance with my invention isarranged between the part which engages the ground, water or deck and the body of the plane and is composed oftelescopic members arranged in the landing gear in a manner such as to landing occurs and which are so formed as to. yieldingly resist the thrust on landing preferably by the simultaneous action {of compressed air and vacuum set up in certain chambers of the device and to prevent sudden rebound preferably by the action of oil or other suitable liquid contained ingthe device, the same serving to cause a relatively slow return to normal position.

The invention may be briefly summarized as consisting of certain novel combinations and arrangementsof parts and details of constructionwhich will be described inthe. specification and claims.

My invention is equally applicable to aeroplanes and seaplanes, for the invention has utility in absorbing shocks due to landing on the ground or other more or less solid landing spots, such as'deck of a ship, or on the water, but for convenience I have illustrated the invention applied to an aeroplane,

Fig. 1 being a front view' of the same; Fig. 2 a side view; Fig. 3 a vertical sectlonal view of the struton a larger scale than in Figs.

1 and 2; Figs. 4, 5 and 6 being cross-sectional views .on a still larger scale substantially ground or deck engaging wheels 13 on the outer ends of axles or rods 14;, the, inner ends of which are connected at 15 to the lower side of the fuselage, this connection being preferably a universal one. From the connection point 15 .the axles. extend downwardly and outwardly,

the outer portions being sub: stantially horizontal. The outer'portions of each axle are connected to the lower wing,

in this instance by two struts 16 and 17 the former being a shock absorbing telescopic strut andthe latter being rigid. When the plane lands the wheels and outer portions of the axle swing upwardly but 'the'rigid struts 17 require them also to swing forwardly, so that there is a composite motion imparted to the axles 14 necessitating a universal connectio n15 between the inner ends of I the axles and the fuselage and universal connections between the telescopic and rigid struts16 and 17 and the parts to which'they are connected. This permits free movement of the parts and relieves the telescopic strut 16 of lateral stresses which, if. existing, would prevent free sliding movement between the telescopic parts.

Taking up now the construction of the telescopic strut, it will be seen by reference to Figs. 3 to 5 that it includes an upper'cylindrical member 18 provided at the top with a cap 19 havinga lug 20 designed to have a universal connection, indicated at 21, with the lower wing of the plane.

The lower part of the cylindrical member 18 is connected by a screw coupling22 to a second cylindrical member'23 which is smaller different diam At the lower part of the cylindrical member 23 is a stufiing box 24.- including suitable v packing and a gland,'anjdslidable throughit 14. and having another e erably the margins of some of is a third cylindrical member or sleeve at the bottom of which is secured a fitting 26 having an eye or opening 21 to accommodate the outer portion of the associated axle or rod e or opening 28 to which the lower end 0 the ri id' strut is adapted to be pivotally connecte At the top of the lower sleeve or c linT drical member 25 is a piston-29 which sli ingly en ages the inner wallof the second cylinrica member 23. This piston,

assembly is detachably connected to the lower cylindrical member 25, may and preferably does consist of several parts or sections clamped together and provided with intervening packing elements, which in this case have upturned margins andmay consist of leather or other suitable material. a

Rigidly attached to the top ofthe piston 29 and extending upwardly therefrom into the upper cylindrical member 18 is a centrally disposed tube 30 and to the upper end of this tube is attached a piston 31 slidingly engaging the inner wall of the upper cylindrical member 18. This piston 31, like iston 29, is

preferably composed of a plura ity of sections clamped to ether and'is provided with a series of space packing elements formed of suitable material, such as leather, I the packing'elements are upturned and others are "downturned so as to form a seal against leakage in either direction past thepiston. The connections between the'tube and the two pistons 29 and 31may be formed in different ways but, inthis instance, the lower end of the tube is screwed into a threaded flange or socket of the lower piston 29 and its upper end is screwed onto a boss onthe lower side of the upper piston 31.

The coupling 22 connecting the cylindrical members 18 and 23 is provided'with a trans;

verse partition 32 having va-central opening through which the tube 30' freely extends.

Additionally, {the partition 32 is provided with avalve which will allow the flow of oil or other fluid through Ithe'partition in one direction only.. In this instance, the valve iscomposed of a 'pluralitg of arc-shaped dr s 33 adapted to be close p tie by ,a movable va member in the form offan annulus 34 which has a seat formed on the upper side'of the partition and is capable 'ofra vertical movement off the seat' limited in this instance'by 'guidepins35 n Liquid is adapted to pass through the valve from the lower side tothe upper side of the partition '32 when the cylindrical members are telescoped inwardly, but when they are extended or given a sliding movement in the opposite direction the. liquid is returned from the upper side to the lower side of the partition 32 through the tube 30, and for this a purpose the tube is provided near itsupper which in this instance for convenience of manufacture and and pref end with an opening or port 36 and near its lower end with a similar opening or ort 37 The fluid is returnedt-hrough the tu I e during the rebound stroke more slowly than it passes upwardly through the ports 33 on the. compression or shock absorbing stroke so that the rebpund ma .be efiectively checked. It is desirable that t e rate-of return move- 'ment following the collapsing due to the impact on landing be made adjustable and, accordingly, the rate of'flow of the fluid through the tube is,'by my invention, made adjustablefrom the exterior of the device. In this instance this is accomplished b means which admits of the adjustment of t e efie'ctive' size of the lower port 37 of the tube, said means consisting of a rotary thimble 38 seated 1n the lower art of the tube 30 and in the central part ofthe piston- 29, this thimble having an openin 'or port 39 adapted to bebrought into in l'or partial register with the lower opening or port 37 of part of the thimble'has a rod-like extension. 40 extending through a stufling box 41 provided on the lower central part of piston 29 and this rod extends down through the cylindrical member 25' to near its lower end.

Means is prov1ded for turning or adjusting thetuber The lower rod 40 and thimble 39 and in this instance this thumb nut screwed on the outer end of the 'lever and a shoulder 45 formed on the lever and engaging 'theinner wall of-the cylin-' drical member 25. -When the thumb nutis loosened the lever so-as to turn the'rod 40 and the thimble 39 at its upper end, thusadjustingthe effective size of the lower. opening'37 formed in tube 30..

' It will be seen inders .18 they are joined by, the' flange coupling 22 constitute one rigid member and that the lower cylindrical member 25 with itspisto'n 29, the tube 30 and; the upper piston 31 in effect constitute a second rigid member slid- 42 can be swung laterally,

from the above that the cyl= and 23,1 reason of the fact that.

able in or telescopically disposed with respect to the first named rigid member.

This construction forms an u ,A between the "piston 31 an the head or a "c amber B between-the, piston 31/ and the partition "32 carrying the valve 34,- also, a third 32 and the lower piston 29, also a chamber lindrical members'23 and 25. i These chainor size as the telescopic action takes place;

chan'iber"C between the partition "additionally, of course,-there isa chamber.

per chamber 1 12a upper end of the cylindrical member 18,- also D between the concentri a zo t 9yin the lower cylindrical member between the piston 29 and the-fitting 26'but'the capacity of this chamber is unchanged and it does not function in the normal use of thedevice.

prior to the application of the compressed air and oil which are employed for the proper operation of the vdevice. In this condition the parts of the telescopic. strut will be collapsed to the maximumextent, the cylindrical member 25 being now-well up in cylindri-' cal member 23 and the pistons 31 and 29 being more or less close to the upper ends of the chambers A and .C. A quantity of oil is first supplied to chamber A, the same u-being indicated by the reference Character 46, so as to, at all times, cover the piston 31- and form a seal, and suflicientccmpressed air is admitted to the chamber A to force the piston 31 downward to the extreme lower end of the cylindrical member 18, the piston coming to rest on the partition 32 of the flange coupling 22. The oil and compressed air can be admitted to chamber A through:

a suitable valve connection 47 shown in Fig. 3.' With the piston 29 now well down in the cylindrical member 23 a quantity of oil is admitted to chamber .C through one or chamber chamber B is larger than that of chamber more normally closed inlets, indicated at 48, in this instance extending through coupling 22. This oil is indicated in'Fig. 3 by reference character 49. The pressure in chamber A is now relieved somewhat by manipulation of the valve connection47, in order to bring the parts into the relation substantially as shown in Fig. 3. The device is now ready for action. p

As explained above,'with the device subjected to the weight of the plane, the tele-v scopic members are partially extended, as indicated in Fig. 3, by air pressure supplied to chamber A. When the impact occurs on landing the parts are telescoped, the pistons 29 and 31 traveling upwardly in the cylindrical members 23 and 18, respectively.

When this occurs the oil in chamber C.

passes free By through the valve ports 33 into but the cross-sectional area of C. and, consequently, the oil will not'travel upward in chamber B as rapidly as the plston 31 moves upwardly. Consequently,

not. only is theair in chamber A compressed but a vacuum is produced 1n chamberbetween the bottom of piston-31 and the top of the body of oil forced up inchamber B.

Consequently the telescopic. action occurring on impact is opposed by the compression of theair in chamber A, by the vacuum iduced beneath piston 31 and-by the vacuum tend to return the partstonor mal position but after the vacuumibeneath the-piston 31 is relieved by a certain downward movement 'of the' piston, the further movement of the parts to normal-position is checked by the. flow of oil from chamber B to chamber C through tube 30. f

The fact that a vacuum is produced above the oil level in chamber B is an important feature of the invention, for not only does the vacuum produced in this chamber resist the compression strokeor impact but it is useful in preventing serious shock to the plane if a series'of impacts occur in rapid succession as may occur if the wheels ride off the ground after the first impact or if they should meet an obstruction immediately upon engaging the ground or deck. By way of explanation of this feature or advantage it mightbe stated that if chamber iB is solidly filled with oil at the end of the compression stroke and if the returnof the parts to or-to ward normal position were dependent solely v uponv the restricted rate of flow of oil' back material yielding of the shock absorber due a to animpact occurring quickly after the first the chamber B is larger than chamber C and by reason of the fact that there is a vaclmpact. However, by reason of the fact that ing the vacuum; that is to say, immediately following each. impact the piston moves downward so as to relieve the vacuum beneath it'without the necessity of replacing any oil and is thus immediately placed in condition to meet and check a succeeding impact. This quick return in relieving the vac- .uum in chamber B does not have an det rimental effect, the main. return stro e occurring relatively slowly due to the governed rate of'return of oil from chamber B to chamber C. p Just before the upper iston reaches the partition '32 at the close '0 the return stroke the'upper-opening 36 in tube 30 passes be-' neath theipartition. gradually checking the fiow'of oil-into and through the tube until finally the opening 36isclosed entirely, in

which event the piston will seat easily and. quietly onto the oil.

lac

Thus it will be seen that I'have providedstruction wherein the measured or restricted return'of fluid takes place through the stem connecting the pistons, I'do not desire to be confined to this construction for the restricted fluid return may take place through other means. 1 Y I I have illustrated and described the invention as applied to aeroplanes for landingon the groun or deck of a ship but, as previous-. ly stated, the invention has utility in the landing gear for lanes adapted to land on the water in whic event the wheels will be replaced by pontoons or e uivalent devices.

Having thus describe my invention, I claim:

1. A shock absorbin device, comprising a fair of telescopic mem er's, one in the form 0 a cylinder and the other slidable therein and having two pistons en aging the inner wall of the c linder, there eing a cushioning'chamber tween the head of the cylinder and one piston, and a fluld receiving recoil checking space between the pistons, embodying means for retarding the flow of fluid therein in one direction.

2.- A shock absorbing device, comprising a cylinder having POItIOIIS -Of two different diameters and members slidable therein and having pistons engaging the inner walls of thB'POl'tlOIlS of the cylinder of difierent dia-meters, there bein a cushioning chamber between the head 0 the cylinder and one of the pistons, and a fluid receiving recoil checking space between the pistons, embodying means for retarding the flow of fluid therein .in one direction. i

3. A shock absorbin devlce, comprising acylinder, a member sli able therein and having two pistons engafgin the inner wall thereof, there being a ui containing space between the pistons, the parts being so formed that upon the. compression or collapsing stroke the volumetric capacity of sand 5 ace is increased.

' 4.- 'shock absorbin device, comprising a cylinder, awall'divi ing the cylinder and having a one-way valve, a member slidable in thecylindcr and havingtwo pistonsv one on each side of said well.

a 5. A shock absorbing device, comprising a cylinder having portions of different diameters separated by a wall having a one-way valve therein, a member slidable in the cylinder and havin pistons on opposite sides of said wall and aving a stem connecting the pistons and passin through the wall.

6. A shock absor ing device,- comprising a cylinder havin portions of different diameters separate y a wall having a valve opening, a member slidable in thecylinder and having pistons. on opposite sides of said wall and having a stem connecting the istons and passing through the wall, auid between the pistons and adapted to be transferred from one side of the wall to the other from the ortion of smaller diameter to the portion 0 larger diameter on the compression or telescopic stroke.

7. A shock absorbing device comprising a cylinder divided by a transverse wall havinga one-way valve, a member slidable therein and having two pistons and a stem connecting them v aiid passing throu h the wall, a"

fluid in the cylinder between t e istons, said valve ermitting the transfer 0 fluid from one si e of the wall to the other on the compression or collapsing stroke,

8. A shock absorbing device comprising a cylinder divided by a transverse wall having a. one-way valve, a member slidable therein and having two pistons and a stem conuecting them and passing through the wall, a fluid 1n the cyhnder between the istons, said valve permltting the transfer of fluid from one side of the wall to the other on the com pression or collapsing stroke, and means permitting a relatively slow return of the fluid durin the rebound stroker 9. shock absorber comprising a cylinder pistons engaging the cylinder on opposite sides of said wall, a hollow stem connecting thepiston and having ports or openings for stem connecting the pistons and having means for the return of fluid to the portion of the cylinder of relatively small diameter independentl of the valve. I

11. A shoc absorber, comprising a cylin der having a transverse partition containing a valve, a member slidable in the cylinder and having pistons engaging the cylinder on opposite sides of the partition, :1 hollowstem connecting the pistons and having openings for the return of displaced fluid and. means for adjusting the rate; of flow therethrough.

12. Ashock absorber'comprising a cyhnhaving a dividing wall with a one-way valve, a member slidable therein and having two der having a dividing partition provided with a valve, a member slidable in the cylinder and composed of pistons engaging the I cylinder on opposite sides of the partition, 9. j liquid between the pistons'and adapted to be transferred from one side of the partition to the other on the compression or collapsin stroke, a stem connectingthe pistons and having openings for the return of liquid 1 during the rebound stroke, and means-acces sible from the exterior of the device for adjusting the rate of flow through the stem.

13. A shock absorbing element composed of relatively 'slidable members having a cushioning chamber and a fluid containing portion w1th means for permitting recoil'at a rate determined by airestricted flow offluid, and means whereby the first portion only of the recoil movement is relatively free and 59 independent of the fluid flow.

14. A shock absorbing strut composed-of relatively movable parts provided with a cushioning chamber and a compartment containing a liquid, together with means whereby on the cushioning stroke the liquid'is-transferre'd relatively freely from one part of the compartment to another and on the return I stroke relativel slowly, the cushioning stroke being resisted y compression in said chamso her and by vacuum created in said compart ment. I I p In testimony whereof, I hereunto aff'n: my signature. JOHN F. WALLACE. 1 v 

